In automotive applications of the LiDAR technology, traditionally the LiDAR is mounted atop of the vehicle. This arrangement has been very functional, but produced a very odd-looking vehicle. In addition, this may cause problems like close-range dead angular zones, exposure to dust and precipitation, and hard-to-reach electrical wiring of the LiDAR sensor. In contrast, integrating the LiDAR sensor into the headlight system would solve these issues . Based on a smart algorithm that combines signals from LiDAR and a CCD image, a smart ON/OFF switching of the laser headlights was demonstrated . However, the integration of LiDAR and CCD required many optical components resulting in complicated assembly and high cost. This paper presents a patent pending optical design of a LiDAR system integrated together with an intelligent headlight system using a single DMD. This integrated design uses the capability of the DMD in both the +12° and -12° positions. The micro-mirrors will be switched between +12° and -12° positions without stopping at the 0° position for all its functions. The headlight light source is placed at the -24° position and the LiDAR detector is placed at the +24° position. Pulsed laser will be used for broad area illuminations for LiDAR operations. The targets in front of vehicle will be scanned and the headlight can be programmed to illuminate the selected areas.
While LEDs have been the used in many of the high “lumen” applications, they are not “bright” enough for projectors, entertainment spotlight, etc., where the etendue of the systems are small. Laser phosphor system have been developed in the last 10 years using mostly silicone, some ceramic and glass, phosphors for low power applications. For higher power systems such as projectors, phosphor wheels are used so as to dissipate the heat in a larger area, allowing the operating temperature to be below the damage and droop threshold of the phosphor material. For silicone phosphor, the outputs are usually limited by the bonding materials. This paper presents static, without a rotating wheel, high power laser excited crystal phosphor system in which the crystal phosphor has a very high damage and drooping threshold temperature. Using 2 laser diode arrays, a total of 170 W of blue laser light is focused into an area of smaller than 2 mm in diameter, giving a power density of over 54 W/sq. mm., which is limited by the available laser power. It is expected to increase in the near future with higher power laser sources, development of homogenizing and diffusing optics at the input, and micro and photonic structures at the output surfaces. For projector applications, this high power static crystal phosphor system can replace the current phosphor wheel, in most case, directly without redesign of the other projector components in terms of mechanical, optical, and electronics. The crystal phosphor materials have been developed and manufactured by Taiwan Color Optics, Inc.
Lidar, radar, optical imaging and ultrasonic are important environmental sensing technologies in the field of autonomous driving. Among them, the radar can perform long-distance sensing, however it is limited by the resolution and cannot distinguish objects. Optical images have clear object resolving power, but hardly to get distance information. Ultrasonic only detect objects that are in very short distances. Therefore, it is necessary to have a technique that can clearly distinguish the objects and get the object information such as speed and distance at medium-range (100-m) for autonomous driving scheme entering level 4 and level 5.
The existing light technology in the autonomous driving is to place the Lidar module on the roof of a car and perform environment sensing in a rotating manner. Such technology has low sensing capability and is not conform to the development direction of the vehicle industry that not fulfill the demand of autonomous car. In contrast to Lidar module on the roof, placing the Lidar on the front of the car has many advantages, such as easy to collect dust, suffer water corrosion and difficult to set up the electrical system. Integrating the Lidar with headlight system is a feasible direction to solve the aforementioned problems. In this study, we will develop laser headlights system with Lidar module by integrating the optical system of Lidar into headlight a unit, in which the smart laser headlight was achieved by feedback control orders system.
The laser headlight will focus on the development of smart headlights with laser as the light source. With the feedback of the system, it can control the car's light field, avoid high-reflection areas at night. The integrated Lidar module will develop a quasi-static optical scanning system with a wavelength of 1550 nm and embed it in the optical path of the laser headlight. By wavelength differences, the optical path of Lidar does not interfere with headlight and high quality optical data could be obtained. Despite adapting 905 nm as optical wavelength in the current technology, the 1550 nm wavelength selected by this study meets the safety regulations and will not cause damage to the human eye at night or during the day. In this study, we will develop a Lidar module attached to a 10W laser headlight for autonomous driving. The simulation and optical performance of integration of Lidar module with laser headlight will be presented.
Automotive headlight evolved from incandescent, to halogen, to xenon, to LED, and most recently, to laser phosphor lamps with increasing efficiencies and brightness. This paper presents the development of laser phosphor headlights using glass phosphor and single crystal phosphor for efficient and high power operations. Laser diodes are used for pumping the phosphors producing the white light to be projected to the roadway. In addition, various configurations of the laser diodes, which are individual addressable, are to be presented. Together with the used of DLP and LCD imagers, intelligent headlights are developed with the abilities selectively scanning the imagers illuminating the roadway with varying intensities. The design of the systems and the experimental results will be presented.
The most widely used light sources for projection system and spotlights are discharge lamps. With tremendous advancements over the last decade in blue laser developments, laser excited phosphor systems have been developed for various applications including projectors and spotlights. One major challenge remains in the very high power applications where multi-kilowatt xenon lamps are still being used. In this paper, an advance material, namely, single crystal phosphor has been developed with high optical efficiency, high power handling capability, and a melting point of 1,950°C. To enable such single crystal phosphor to be used to its full capacity, a major effort was placed on the heat sinking of the crystal phosphor pumped at high power, over 70 W of blue laser power from a 4 by 6 array of laser diodes. The nominal dimension of the crystal phosphor of one of the system measures 2 mm by 2 mm by 4 mm and is end-pumped from one end with a set of focusing lenses directing the output from 24 lasers onto the surface of the crystal phosphor. The 4 sides of the crystal phosphor is specially coated and attached to the heat sink for efficient dissipation of heat, keeping the temperature of the crystal low enough for efficient emission. The output from the crystal phosphor is extracted using a CPC reducing the total internal reflection effect inside the crystal phosphor. To accommodate the high power laser at the input face of the crystal phosphor, various methods are used to prevent the local burning of the input face, including the use of diffusers, light pipes, and light tunnels. The computer simulation and experimental results will be presented.
Traditional illumination systems uses various lamps selected based on certain requirements of the applications. One common issue is the trade-off between output brightness and lamp lifetime. LEDs with long lifetimes have been used in many applications. This paper describes a multi-colored LED illumination system with individually controlled red, green, and blue outputs combined together with the etendue of a single LED, having enhanced green and red output brightness with supplementary excitation of the phosphor-based green and red LEDs from additional blue LEDs, increasing the overall output of the system.
We report and demonstrate the feasibility of adapting glass as a phosphor-converted layer in laser headlight module, instead of conventional doped silicone that can potentially provide higher reliability and better performance for advanced laser headlight module. A laser headlight module (HLM) consists of blue a high-power laser array, a color phosphor, and an optical micro-lens system. The color phosphor is a key component in the HLM which consists of glass-based yellow phosphor-converted layer. The conversion layer of the yellow Ce:YAG phosphor is bonded on an aluminum substrate. A blue high-power laser array is used to excite the color phosphor and then release yellow light. Then, the combinations of blue and yellow light become white-laser light for use in the HLM. In this study, the fabrication of HLM with the glass-based yellow phosphor-converted layers is presented. The optical performance of the HLM including lumen, lumen efficiency, chromaticity, and transmission is detailed discussion. This study demonstrates the adapting glass as a phosphor-converted color phosphor in the HLMs that provide high-reliability and better performance for use in the new-generation laser headlight module.
A new scheme of high-reliability laser light engine (LLE) employing a novel glass-based phosphor-converted layer is proposed and demonstrated. The LLE module consists of a high-power blue light laser array and a color wheel, which includes two glass-based phosphor-converted layers of yellow Ce:YAG and green Ce:LuAG and a micro motor. The combinations of blue, yellow, and green lights produce high-purity phosphor-converted white-laser-diodes (PC-WLDs). The lumen degradation and chromaticity shift in the glass-based phosphor-converted layer under different laser powers are presented and compared with those of silicon-based PC-WLDs. The results showed that the glass based PC-WLDs exhibited in lower lumen loss and less chromaticity shifts than the silicon-based PC-WLDs. The long term reliability study evaluation in glass- and silicone-based PC-WLDs under high-power 120 W at room temperature for 20,000 hours is also presented and compared. The result showed that the silicone-based PC-WLDs exhibited 50% in lumen decay which failed in operation, while the glass-based PC-WLDs only exhibited 2% in lumen decay. This indicates that the proposed LLE modules are benefit to employ in the area where the silicone-based material fails to stand for long and strict reliability is highly required. This study demonstrates the advantages of adapting novel glass as a phosphor-converted color wheel in the LLE modules that provide unique high-reliability as well as better performance for use in the next-generation laser projector system.
A highly reliable laser light engine (LLE) employing a novel glass-based phosphor-converted layer is experimentally demonstrated. The LLE module consisted of a blue light laser array and a color wheel, which included two glass-based phosphor-converted layers of yellow YAG:Ce and green LuAG:Ce and a micro motor. The blue light laser array was used to excite the color wheel to create yellow and green lights. The combination of the blue, yellow, and green lights produced high-purity white light for use in LLEs. The glass-based LLE exhibited better thermal stability, higher luminous efficiency of 64.7lm/W(YAG:Ce) and 67.2lm/W (LuAG:Ce), and higher purity of 95.4%(YAG:Ce) and 77.4%(LuAG:Ce). This study clearly demonstrates the advantages of adapting novel glass as a phosphor-converted color wheel in LEL modules that provide higher reliability and better performance of laser projectors for use in the next generation LLEs, particularly in the area where the conventional LLEs employing silicone-based phosphor fails to stand for long and strict reliability is highly required.